1. Technical Field
The present invention is directed generally toward a method and apparatus for a data processing system. More specifically, the present invention relates to a computer implemented method, computer program product and data processing system for a storage array with a redundant dual active controller array to appear as two independent storage targets.
2. Description of the Related Art
Currently, when computer applications require high input/output (I/O) data transfer rates between a host system and data storage devices, usually, high performance redundant dual controller storage arrays are used as data storage devices for those applications. The host system will install multiple host bus adapters (HBAs), which are small computer system interface (SCSI) initiators that connect to storage array systems with multiple target ports. A host bus adapter could be a Fiber Channel (FC), InfiniBand (IB), Serial Attached SCSI (SAS), Internet small computer systems interface (iSCSI), Parallel SCSI Interface (SPI) or other transport protocol host bus adapter (HBA) that provides transport connections for small computer system interface (SCSI) protocol. A host bus adapter provides input/output (I/O) processing and physical connectivity between a server and storage devices. As the only part of a storage area network that resides in a server, host bus adapters (HBAs) also provide a critical link between the storage area network and the operating system (OS) and application software. A small computer system interface (SCSI) initiator is a device that begins a small computer system interface (SCSI) transaction by issuing a command to another device, referred to as the small computer system interface (SCSI) target or simply as the target, giving the target a task to perform. Typically, a small computer system interface (SCSI) host adapter is the initiator but targets may also become initiators. In such a hardware configuration, the host can have multiple data paths to a data volume in the storage array. Data paths are combinations of host initiator ports and storage array target ports. The set of data paths to the storage array usually will be grouped as two groups. Each group of data paths corresponds to a set of data paths to a specific storage controller in the redundant dual active controllers.
Thus, the host will see all data paths to the various data volumes through each of the redundant dual active controllers, even though each of the redundant dual active controllers only controls a subset of the total number of data paths. As the host systems will see all the paths as viable through each of the redundant dual active controllers, commands may be sent to store or retrieve information to a controller that does not actually have access to the data volume, thus causing errors and delays.